Switching regulators are DC—DC converters that supply a certain voltage independent of changes in the input voltage and can be categorized as the step-up type, which outputs a voltage higher than the input voltage; the step-down type, which outputs a voltage below the input voltage; and the step-up/step-down type. The so-called H-bridge type is also generally known as the voltage step-up/step-down type of switching regulator.
An H-bridge type switching regulator includes an inductive element used for storing magnetic energy, a switching element for controlling the current supply to the inductive element from the power supply voltage, and another switching element for controlling the current output from the inductive element to the load. By controlling the timing for turning each switching element on and off, the amount of magnetic energy stored in the inductive element and the amount of the electrical amount energy output to the load can be suitably controlled. Therefore, the desired DC voltage can be supplied to the load. An example of which are found in the specification of U.S. Pat. No. 6,087,816 and the specification of U.S. Pat. No. 6,215,286.
However, in a conventional voltage increase/decrease DC—DC converter made from the H-bridge type switching regulator, since the timing for storing and the timing for releasing magnetic energy in the inductive element are completely separate, a large current flows through the inductive element. As a result, the power loss caused by the switching element, inductive element, and other low-resistance components becomes high, and the voltage conversion efficiency is low.